ENCePP Guide on Methodological Standards in Pharmacoepidemiology

4.6.2. Models of studies using multiple data sources

i) Local data extraction and
analysis, separate protocols

The traditional way to combine
data from multiple data sources is when data extraction and analysis are
performed independently at each centre based on separate protocols. This is
usually followed by meta-analysis of the different estimates obtained (see
Chapter 5.7).

This approach requires very
detailed common protocols and data specifications that reduce variability in
interpretations by researchers.

Multi-centre, multi-database studies with common protocols:
lessons learnt from the IMI PROTECT project (Pharmacoepidemiol Drug Saf
2016;25(S1):156-165) states that a priori pooling of data from several databases
may disguise heterogeneity that may provide useful information on the safety
issue under investigation. On the other hand, parallel analysis of databases
allows exploring reasons for heterogeneity through extensive sensitivity
analyses. This approach eventually increases consistency in findings from
observational drug effect studies or reveal causes of differential drug
effects.